Your approach on what defines a role-playing game seems quite limited.
You apparently accept that computer games can be role-playing games, but only if they follow the D&D set of rules, more or less.
Yes, so is it.
no computer role-playing game ever published might truly be a role-playing game
Wrong, look at this games: The Might and Magic Serie, Baldurs Gate and so on
Sorry, but that's pretty narrow-minded.
Matter of opinion

It's comparable to multi-classed or dual-classed characters in the D&D system, but simpler and much more adaptable to what the player has in mind.
Multi-classed chars i can play in Divinity 2, but I am sure, all players will ONLY play that.
Also, it is much to simple and it´s not really a system. Right, it gives more Opportunities now, but all make not much sense!
When there was a chance for modding the game, i´m sure, this game will be really great. But this Larian Studios
not like!!
Regards, Marlow